/*
 * Copyright (C) 2011 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.util.concurrent;

import com.google.common.annotations.GwtIncompatible;
import com.google.errorprone.annotations.CanIgnoreReturnValue;

import java.util.concurrent.Callable;

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A listening executor service which forwards all its method calls to another listening executor
 * service. Subclasses should override one or more methods to modify the behavior of the backing
 * executor service as desired per the <a
 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 *
 * @author Isaac Shum
 * @since 10.0
 */
@CanIgnoreReturnValue // TODO(cpovirk): Consider being more strict.
@GwtIncompatible
@ElementTypesAreNonnullByDefault
public abstract class ForwardingListeningExecutorService extends ForwardingExecutorService
        implements ListeningExecutorService
{
    /**
     * Constructor for use by subclasses.
     */
    protected ForwardingListeningExecutorService()
    {
    }

    @Override
    protected abstract ListeningExecutorService delegate();

    @Override
    public <T extends @Nullable Object> ListenableFuture<T> submit(Callable<T> task)
    {
        return delegate().submit(task);
    }

    @Override
    public ListenableFuture<?> submit(Runnable task)
    {
        return delegate().submit(task);
    }

    @Override
    public <T extends @Nullable Object> ListenableFuture<T> submit(
            Runnable task, @ParametricNullness T result)
    {
        return delegate().submit(task, result);
    }
}
